1. Field of the Invention
The present invention relates to a method of producing a plurality of equal printed circuits on a common, planar insulating carrier of which at least one surface is provided with an electrically conducting layer, and relates specifically to such a method of producing oscillating circuits of which every one includes an electrical circuit closed in itself and having spirally arranged conductor tracts forming at least one induction coil and including at least one capacitor.
Accordingly, the present invention relates specifically to a novel method of producing such electrical oscillating circuits which the longer the more are used for specific applications in a large variety of industrial fields. Such electrical oscillating circuits are applied among others for a supervising and recognizing of moving objects in which the possibly emitted signals are utilized for an initiating of further process steps, e.g. control signals. If an electrical oscillating circuit or resonant circuit of mentioned structure and predetermined frequency is mounted to an object, such object can be monitored regarding its sequence of movements and be controlled accordingly.
An exemplary application is a controlling of railroad cars, specifically freight cars which are shunted via switches according to their specific points of destination.
The decisive point of such applications is that the oscillating circuits are at the one hand low cost items and, more important, feature at the other hand a high accuracy of frequency and excellent quality of the coil such that an erroneous sorting and mis-directions can be avoided with a high degree of accuracy.
The oscillating circuits under consideration regarding this invention are structured basically as follows:
On one surface of a planar carrier made of an electrically non-conductive material (a dielectric) there is provided a conductor spiral which is formed by spirally arranged conductor tracts which form the respective inductor coils of the oscillating circuit which in turn are electrically connected to one or several capacitors or one or several electrically conducting surfaces forming a respective portion of a capacitor. At the other side of the carrier correspondingly structured and planarly aligned electrically coonductive and mutually interconnected surfaces are provided which operate as the counterparts of the respective capacitor. The electrical conduits of the one of the sides are connected to those of the other side at a suitable point to complete the electrical circuit.
It has been mentioned above that the electrical conduit tracts of one of the sides act as induction coils of the oscillating circuit and that the larger conductive surfaces serve together with the corresponding surfaces of the other side and the intervening dielectric as capacitors. The complete electrical circuit, comprising the induction coils and one of the capacitors are tuned or adjusted, respectively to a predetermined receiving frequency. Oftentimes the oscillating circuits are designed such that a possibly further capacitor is tuned together with a corresponding induction coil to a so-called self-destructing frequency such that the oscillating circuit can be put out of order after an emitting of a signal (by emitting of energy having the self-destruction frequency which e.g. leads to a destruction of a point of connection in the electrical circuit).
So much regarding the general design of the known oscillating circuits under the present consideration.
It has been mentioned that a broad field of application of such oscillating circuits is only possible if these oscillating circuits made with a maximal operating precision (precision of frequency and quality of coils) can at the same time be manufactured at low cost.
Without any doubts as far as possible automatic series production is demanded. Such series production has, however, until now foundered due to the high demands regarding precision.
2. Description of the Prior Art
Methods of production according to which the circuit patterns are applied onto the carriers or the substrate, respectively by means of a screen printing or a photo engraving have not been successful regarding reaching the sought object due to economical considerations. Such methods are either too slow and demand highly qualified skilled personnel or are too complicated and require additionally specific chemical auxiliary agents.
A recently applied method utilized the etching technique for extricating electrical circuits. Such method allows a comparatively economical production in which a plurality of individual oscillating circuits can be produced simultaneously, indeed, but which requires the demanded highest precision or economical possibility, respectively regarding a later correcting of an oscillating circuit having a performance not within a set tolerance.